As a fluid pressure control device that controls an action of hydraulic working equipment, JP2010-101400A discloses a fluid pressure control device including a cylinder to be extended and contracted by a working fluid supplied from a pump to drive a load, a control valve that switches between supply and discharge of the working fluid to and from the cylinder to control an extending/contracting action of the cylinder, and a load holding mechanism placed in a main passage that connects a load side pressure chamber of the cylinder and the control valve.
The load holding mechanism includes an operation check valve, and a switching valve to be activated by pilot pressure to switch an action of the operation check valve. The switching valve includes three ports of a first supply port to which a bypass passage bypassing the operation check valve is connected, a second supply port connected to a back pressure passage communicating with a back pressure chamber of the operation check valve, and a discharge port communicating with a control valve.
The switching valve can be switched to three switching positions of a blocking position, a first communication position, and a second communication position in accordance with a moving amount of a spool changed by pilot pressure, and the ports are opened and closed in accordance with the switching positions.
In a case where the switching valve is at the blocking position, the ports are closed.
In a case where the switching valve is at the first communication position, the first supply port and the discharge port communicate with each other. Thereby, the working fluid of the bypass passage is discharged from the discharge port.
In a case where the switching valve is at the second communication position, the first supply port and the second supply port, and the discharge port communicate with each other. Thereby, the working fluid of the bypass passage is discharged from the discharge port, and the working fluid of the back pressure passage is discharged from the discharge port.